Alloy steels



Patented Apr. 1, 1952 ALLOY STEELS Henry William Kirkby and Charles Sykes, Sheffield, England, assignors, by mesne assignments, to Firth-Vickers Stainless Steels Limited, Sheffield, England, a British company No Drawing. Application November 10, 1949, Se-

rial No. 126,698. In Great Britain December This invention comprises improvements relating to alloy steels.

The invention provides a ferritic alloy steel comprising as essential constituents carbon 0.05 to 0.5%, chromium 4 to 20%, molybdenum up to 3% interchangeable with tungsten up to 3%, columbium up to 2.5%, boron up to 0.5% and vanadium up to 2%.

The invention includes the following range of composition Carbon .05-0.5% Silicon Up to 3% Manganese Up to 4% Nickel Up to 5% Chromium 1.0-20.0% Molybdenum Up to 3% (interchangeable with tungsten) Vanadium Up to 2% Tungsten Up to 3 (interchangeable with molybdenum) Columbium Up to 2.5% Nitrogen Up to 0.25% Boron Up to 0.5% Cobalt Up to Iron Remainder The preferred proportions of the various constituents are as follows:

Carbon .10 to .25% Silicon 0.5 to 1.5% Manganese 0.5 to 1.5% Nickel 0.5 to 1.5% Chromium 10.0 to 14.0% Molybdenum 0.5 to 1.5% Vanadium 0.1 to 0.3% Tungsten 1.0 to 3.0% Columbium 0.5 to 1.25% Nitrogen 0.10 to 0.15% Boron 0.025 to 0.10% Cobalt Nil to 5% Iron Remainder The product according to the invention is a iorgeable ferritie steel possessing exceptionally high creep resistance at temperatures at least up to 700 C. The special feature of the present steel is that it is a ferritic type that is to say it is magnetic, can be hardened and tempered and has thermal expansion properties similar to those of carbon and low alloy steels. Ferritic types of steels, as a class are generally regarded as being inferior in creep resistance to austenitic steels, but the steel of this invention is superior 2 Claims. (Cl. 75-126) 2 to several known austenitlc alloys at temperatures of 600-650 C.

Ferritic steels have the advantage for high temperature applications because of the lower thermal expansion characteristics (cf. austenitic steels).

The high tensile and proof properties of the present steel are also desirable features for many high temperature applications, particularly in jet engines and gas turbines.

The steel of the invention possesses excellent scale resistance up to at least 750 C.

After suitable heat treatment of steels according to the present invention the following typical high temperature properties have been obtained:

Rupture Test Tem- Stress perature g ff C. 15 tons/sq. in 650 463 Percent Stress fi g Deformation in 300 hrs.

C. 18 tons/sq. in 600 .4 10 tons/sq. in 650 24 Suitably selected alloys within the invention also have high resistance to softening at elevated temperatures as judged by room temperature hardness.

The special properties of the alloy according to the present invention are believed to be due to the combined effect of carbon, molybdenum, columbium, boron and vanadium. The columbium and carbon contents are of particular importance, but the combination of all five elements within the range of proportions set out herein is necessary in order to produce an alloy steel having the particular advantageous characteristics described herein.

We claim:

1. A forgeable ferritic alloy steel possessing high creep resistance at temperatures at least up to 700 C., and having a composition characterised by the absence of nickel above a proportion of 1.5% and by the presence as essential constituents of 0.05-0.5% carbon, 4-20% chromium, 0.5-3% molybdenum interchangeable at least in part with tungsten, an effective proportion up to 2.5% columbium, an effective proportion up to 3 4 0.25% nitrogen, an effective proportion up to REFERENCES CITED 0.5% boron, (ll-2% vanadium, and the balance The following references are of record in the substantmny file of this patent:

2. A forgeable ferritic alloy steel as claimed in claim 1 comprising carbon 10-25%, silicon UNITED STATES PATENTS 0.51.5%, manganese 0.51.5%, nickel 0.51.5%, Number Name Date chromium 10.0 4.0%, moly d n m 05-15%, 2,432,616 Franks et al Dec. 16, 1947 vanadium 0.1-0.3 tungsten Lil-3.0%, colum- 2,432,617 Franks et a1 Dec. 16, 1947 bium 0.5-1.25%, nitrogen 0.10-0.15%, boron 0.025-0.10%, cobalt in an efiective proportion up 10 OTHER REFERENCES to 5%, and the remainder substantially all iron. Alloys of Iron and r um, V L 2, Hi h Chromium, page 94. Edited by Kinzel and HENRY WILLIAM KIRKBY. Franks. Published in 1940 by the McGraw-Hill CHARLES SYKES. BOOk C0., New York. 

1. A FORGEABLE FERRITC ALLOY STEEL POSSESSING HIGH CREEP RESISTANCE AT TEMPERATURE AT LEAST UP TO 700* C., AND HAVING A COMPOSITION CHARATER ISED BY THE ABSENCE OF NICKEL ABOVE A PROPORTION OF 1.5% AND BY THE PRESENCE AS ESSENTIAL CONSTITUENTS OF 0.05-0.5% CARBON, 4-20% CHROMIUM, 0.5-3% MOLYBDENUM INTERCHANGABLE AT LEAST IN PART WITH TUNGSTEN, AN EFFECTIVE PROPORTION UP TO 2.5% COLUMBIUM, AN EFFECTIVE PROPORTION UP TO 0.25% NITROGEN, AN EFFECTIVE PROPORTION UP TO 0.5% BORON, 0.1-2% VANADIUM, AND THE BALANCE SUBSTANTIALLY IRON. 